There have been many kinds of authentication devices whose biometric measurements are taken from the fingerprints of living individuals. In recent years, blood vessels of living individuals are regarded as one of the targets for biometric authentication.
This kind of authentication devices takes an image of blood vessels by using near-infrared rays: The main absorbers of near-infrared rays in the blood vessels are deoxy-hemoglobin (venous blood) and oxy-hemoglobin (arterial blood). The authentication device then registers the resultant blood vessel image in a memory as data to be compared with the other, or checks it against data or blood vessel images registered in the memory (see Patent Document 1, for example).
Patent Document 1 Japanese Patent Publication No. 2004-178606.
However, since the above authentication device just stores the resultant blood vessel image in the memory without processing it, there is a problem that a large amount of space in the memory is occupied by one-person blood vessel image.
One way to solve the problem is to find out the bifurcation points of the vessels from the blood vessel images to be stored in the memory as a blood vessel pattern. This method, however, reduces the accuracy of authentication because it only checks up the bifurcation points.